Yes, there is a program to manage init scripts and run levels. I think. Again, I don't really use Ubuntu much, I just find Gentoo easier, so I may be wrong. Maybe one of the Ubuntu people can answer how they handle run levels and init scripts.
Essentially Linux has what are called run levels. When a computer starts up it goes to run level 1 and executes the scripts associated with that run level, then 2, etc. Different levels are associated with different functionality. In many distros, runlevel 3 is text only with no gui, while 5 is the full gui interface. 1 is pretty basic, no networking, etc.
You can add and remove init scripts from different run levels, which allows you to have multiple ways you run your system, some leaner and more basic than others. You can change run levels with the "init" command. init 0 is a shutdown, init 6 is a reboot, init 3 is (in many systems) a text only mode, etc. I think Ubuntu made a lot of the run levels the same from 3-5, but not sure.